I developed my 11th C-41 roll in the same Tetenal Colortec C-41 (1 liter) chemicals. The chemicals were mixed back in March 2010 -- over 3 months ago. The colors turned out still fresh and bright. Tetenal recommends that the mixed chems are used for max. 6 weeks and then replaced. I've used same liquids for over twice as long. How long have you been able to use same mixed Tetenal C-41 chemicals? How many films you've been able to develop with same liquids? I could almost swear the colors have become better after every film. Slight over-exposure is because of the exposure meter on my Mamiya M645. Kodak Portra 160VC in 120 format.